“People are typically getting much less protection than they think,” Antony Young, an author of the study and professor of experimental photobiology at King’s College London, told The Guardian.

“For example, if you get SPF20 and use at a lower thickness of 0.75 milligrams per centimetre squared, your level of protection could be as low as SPF4.”

As a result, Nina Goad of the British Association of Dermatologists said, “This research demonstrates why it’s so important to choose an SPF of 30 or more. In theory, an SPF of 15 should be sufficient, but we know that in real-world situations, we need the additional protection offered by a higher SPF.”

In case you need any more convincing, the Cancer Council of Australia recommend coating yourself in sunscreen “that is labelled broad-spectrum, water-resistant and SPF30+ or above”.

What do the various SPF numbers even mean?

SPF stands for ‘sun protection factor’, which isn’t really all that difficult to wrap your head around.

However, there is no shortage of half-truths, rumours and flat-out lies (which we won’t list here, so as to save on any confusion) about what the number following those three letters actually means.

The number indicates what fraction of the sun’s harmful UV rays can reach you through the sunscreen.